Brake-shoe.



W. H. SA'YEE,

BRAKE SHGE.

Mmm-mun mio ma. 24, 1913.

during casting. Frequently it is sufficient merely to press the pieces slightly into` the sand, su'fliciently to prevent their floating when the metal is poured. In manufacturing the form of brake shoe shown in Fig.l 10, abrasive material should be located 'not only oppositel the wheel tread but also opposite `the Wheelflange, as clearly indicated in Figs..2,'7 and Saat lla.

Preferably instead of having a single insert of great area 'or length, I employ a se ries of detached inserts, as clearly indicated inA Figs. 2 and l0, and their size may be d`ey creased and number increased indefinitely,

as desired except that the lumps should not be reducedy below a size which enables them to be securely held in the body of the casting so that, at the same time, a considerable portion of/their surfaces may form parts of theactive'face ofthe brake shoe, and also i that the num-ber and size of the lumps should y y .be,such that' their fexposed surfaces forni only a minor 'pai't, usually about ten perfcent. of the active face of the brake shoe. '2'5 4vpreeialole 'size/arises. from the necessity'of having aeon's'iderable body .anchored in the Tliene'cessity formaking the lumps of apfcasting spl/tliat4 thelump cannot be dragged but off'-itsmatrix by 1the friction of the wheel. This firm anchoring of thelumps is further secured by their naturally highly irregular shape, as shown in the drawings. When large number of fine particles are used 1n the shape of a comminuted mass of the hard material these small particles restv on the surface of the casting andare easily rubbed ofi" by the wheel. This robs the shoe cio of all the hard material so swept away and destroys the cutting action of the shoe on the wheel to that extent. Furthermore, the particles so torn away from the shoe duringV a severe application of the brakes which heats the Wheel, are apt'to embed themselves in the temporarily heat softened tread of the wheel and so transferred become A,so many cutting tools for rapidly cutting up the shoe instead of doing the intended Work of cutting the wheel. The necessity for maintaining the number of lumps used at such a' low figure that the sum of the exposed surfaces ofthe lumps will form only a minor portion of the active surface of the shoe arises from the fact Vthat said shoe is still primarily a friction producing device, and only secondarilv a cutting tool. The primary purpose ofeach shoe application is to stop'the wheel from turning. Incidentally and secondarily, the purpose is to cut away a ininorportiou of the wheel face which is not suilicientlvworn down bv the rail. To produce thefrictiou the maior active portion of the shoe face must still be cast iron, or cast steelas'distinguished from vthose surfaces heretofore solely designed for cutting, polishing, abrading, or resisting wear,

which are wholly terial.

'Ihe mold and the inserts being thus pre pared, the moltencasting' metal which will ordinarily be one of the ferrous metals such ascast'iron, will be poured into the mold,

-composed of hard i nia-' the casting metal thus embedding the abrasive lumps and causing them to become consolidatedin the body or matrix 14, -thus becoming a permanent part of the brake shoe. Owing to the, greater hardness of the abrasive material as compared with the cast iron, it is able to perform its function of `truing the /car wheel as required. Owing to its being of a nature proof against impairment by the high casting temperature, as

well as by the temperature and hard 'usage of actual' service, the abrasive lumps are -uninjuredfand are able to effectively serve their function.

.Generally speaking, it may be said-that fthe abrasive material may be located .in .the

vv\vshoe y.at any desired 'point suitable to'v the.' y

is at' that poiiit where the protuberance tends'to form, so that the tread of the wheel is kept approximately?,cylindrical, and the growth of the potuherance. is prevented. In such cases as this where the wheel has the ordinary flange, a second portion of abrasive material is desirable inorder to grind down the wheel flange thus soy preventing the fiange from extending excessively beyond the wheel tread as the wheel wears. Such additional abrasive maiio terial isshown at ll lObviously for difier f ent conditions the location of theabrasive materialcan be altered. Thus, sometimes it iS found that with particular conditions fthe Wheel 16.will wear as indicatedl iri'Fig.' 5,

and in that case the brake shoe shouldfbe A' provided with abrasive material as shownin Fig. 8. In the case of locomotivesv with.'

three or more driving wheels, sometimes the middle wheel i7 is unfianged and the wear in ysuch case may be as in Fig. 6. 4To meet this situation, abi-alte shoe, as in Fig. 9,

may be employed. is thatr as long as there is any false flange In any case,- the action upon the wheel tread the tendency toward its formation is offset by the wear produced by the abrasive alundum pieces 11. At the same time, the presence of the alundum in the brake shoe increas the braking acfi Sesma mii 1. A 4 :i l :fu n D nu WTA. my. a a A l. n B, ,.Hnl a .all C .i i 2 Y 4, 

